Along with the development of digital technology, recent years have seen a further increase in functionality of electronic devices such as mobile information devices and information home appliances. Accordingly, there is an increasing demand for a nonvolatile memory device with a higher capacity, lower power consumption for writing, a higher speed of write/write time, and a longer product lifespan.
In response to such a demand, for example, research and development of a nonvolatile semiconductor memory device which includes a memory element configured using what is called a variable resistance memory element is under way. The variable resistance memory element indicates an element which has a resistance value changing according to electrical signals, has properties of keeping the resistance value even when the electrical signals are no longer supplied (that is, keeping the resistance value in a nonvolatile manner), and is capable of storing data using a change in this resistance value.
Representative examples of the variable resistance memory element include a magnetic random access memory (MRAM), a phase change random access memory (PRAM), a resistance random access memory (ReRAM; a variable resistance element), and a spin transfer torque random access memory (SPRAM).
As an example of the structures of the nonvolatile memory devices which include these variable resistance memory elements, a cross-point structure is known. In the cross-point structure, the memory cells are arranged in an array (which is hereinafter referred to as a cross-point cell array). More specifically, memory cells are arranged each of which is located at a cross-point between a bit line and a word line that are perpendicular to each other; the memory cell is located between the bit line and the word line.
In the cross-point structure, to change (write) a resistance value of a memory element included in a target memory cell, a voltage is applied to a corresponding set of the bit line and the word line, which not only causes a current corresponding to the voltage applied to the memory cell to flow through the write target memory cell, but also causes a current (sneak current) to flow through the write target memory cell via the other unselected memory cells which are connected in series or in parallel to the selected memory cell that is the target memory cell. Since the sneak current changes a current necessary to change resistance of a memory element included in the write target memory cell, the sneak current impairs a reliable operation of write (resistance change operation) in the nonvolatile semiconductor memory device.
Patent Literature 1 discloses a method for compensating a voltage drop in the memory cell to stabilize a write operation of a cross-point cell array.